Production of bactericidal concentrations of hydrogen peroxide by Streptococcus sanguis

Abstract

Streptococcus sanguis possess a bacteriocin-like activity against related bacteria and Gram-positive filamentous and diphtheroidal organisms in vitro. This activity was associated with the alpha-haemolysis produced by Strep. sanguis. During aerobic growth conditions, Strep. sanguis liberates hydrogen peroxide. Reduced oxygen tension and the enzymes catalase and peroxidase abolish bacteriocin-like activity, alphahaemolysis and peroxide production. Bacteriocin-like activity of Strep. sanguis is due to liberated peroxide and is identical with alpha-haemolysis. No other haemolytic or bactericidal substances are demonstrated. Variability in sensitivity to the inhibitory action by Strep. sanguis is related to catalase activity of sensitive strains. The potential for a bactericidal activity in vivo by Strep. sanguis due to secretion of hydrogen peroxide is reviewed. Since Strep. sanguis is the dominant organism in early dental plaque, the role of peroxide is discussed in maintaining a balance of the indigenous dental plaque flora.